1. Field of the Invention
The present invention relates to a cooling unit adapted for use in an auger type ice making machine, a freezing mechanism of an ice creamer or a freezing mechanism of the other type cooling equipment.
2. Description of the Prior Art
Disclosed in Japanese Patent Laid-open Publication No. 11 (1999)-132610 is a cooling unit used in an auger type ice making machine, wherein a metallic freezing pipe is helically wound on the outer periphery of a metallic cylindrical evaporator housing through a metallic filler for thermal contact with the evaporator housing. In the cooling unit, the metallic filler is embedded in a helical clearance between the evaporator housing and the freezing pipe to enhance the heat-exchange efficiency of the cooling unit.
It is, however, difficult to completely deposit the metallic filler into the helical clearance between the evaporator housing and the freezing pipe. If the metallic filler is partly chipped, an undesired clearance is formed between the evaporator housing and the freezing pipe. In addition, if the metallic filler causes corrosion of the evaporator housing at its embedded portion, there will occur an undesired clearance at the corroded portion of the evaporator housing. In such an instance, the air in the clearance is repeatedly expanded and contracted in operation and stopping of the cooling unit, and water entered into the clearance from the exterior is repeatedly frozen and melted in operation and stopping of the cooling unit. This results in enlargement of the undesired clearance between the evaporator housing and the freezing pipe and progress of the corrosion of the evaporator housing. The enlargement of undesired space in communication with the exterior causes local damage of the freezing pipe, resulting in leakage of refrigerant flowing therethrough and deteriorates the cooling performance of the unit.